Exhaust aftertreatment systems are used to receive and treat exhaust gas generated by IC engines. Conventional exhaust gas aftertreatment systems include any of several different components to reduce the levels of harmful exhaust emissions present in exhaust gas. For example, certain exhaust aftertreatment systems for diesel-powered IC engines include a selective catalytic reduction (SCR) catalyst to convert NOx (NO and the NO2 in some fraction) into harmless nitrogen gas (N2) and water vapor (H2O) in the presence of ammonia (NH3).
Many aftertreatment systems include a particulate filter (e.g., a diesel particulate filter) positioned upstream of the SCR system. The particulate filter is configured to filter particulate matter, for example soot entrained within the exhaust gas flowing through the aftertreatment system to meet particulate emissions regulations. Exhaust emission regulations require monitoring of the particulate filter to ensure that the particulate matter emissions meet regulation standards. Malfunctioning of the particulate filter, for example a crack in the particulate filter can cause excessive particulate matter to flow to downstream aftertreatment components (e.g., the SCR system) and into the environment.
Various conventional aftertreatment systems include a particulate matter sensor positioned downstream of the particulate filter. The particulate matter sensor can include a resistive sensor which monitors the amount of particulate matter flowing downstream of the particulate filter. Such resistive particulate matter sensors generally have low durability (e.g., operational lifetime on a vehicle of less than 10,000 miles), are susceptible to contaminants and have a low signal to noise ratio. Furthermore, the data obtained from particulate matter sensors is complex and difficult to analyze for determining the actual concentration of particulate matter flowing downstream of the particulate filter.